The term person perception refers to the different mental processes that we use to form impressions of other people.
This includes not just how we form these impressions, but the different conclusions we make about other people based upon our impressions.
When you meet with a new co-worker, you immediately begin to develop an initial impression of this person.
When you visit the grocery store after work, you might draw conclusions about the cashier who checks you out, even though you know very little about this person